Method of making optically fused semiconductor powder for solar cells

ABSTRACT

A method and apparatus for forming semiconductor particles (42) for solar cells using an optical furnace (30). Uniform mass piles (26) of powered semiconductor feedstock are almost instantaneously optically fused to define high purity semiconductor particles without oxidation. The high intensity optical energy is directed and focused to the semiconductor feedstock piles (26) advanced by a conveyer medium (16) thereunder. The semiconductor feedstock piles (26) are at least partially melted and fused to form a single semiconductor particle (42) which can be later separated from a refractory layer (18) by a separator (50), preferably comprised of silica. The apparatus (10) and process is automated, providing a high throughput to produce uniform mass, high quality spheres for realizing high efficiency solar cells. The apparatus is energy efficient, whereby process parameters can be easily and quickly established.

CROSS REFERENCE TO A RELATED APPLICATION

Cross reference is made to Co-pending patent application Ser. No.08/323,317, entitled "Process for Producing Semiconductor Spheres",filed Oct. 14, 1994.

TECHNICAL FIELD OF THE INVENTION

This invention relates generally to photovoltaic solar cell arrays, andmore particularly, to a method and apparatus for efficiently producingsemiconductor spheres of uniform mass for use in a solar cell array.

BACKGROUND OF THE INVENTION

Solar cells are photovoltaic devices which convert the sun's solarenergy into useful electrical energy. These solar cells typicallycomprise a matrix or array of doped semiconductor spheres embedded in alight-reflective aluminum foil, the semiconductor material typicallycomprising silicon. One such solar cell is disclosed in U.S. Pat. No.5,028,546 to Hotchkiss, entitled "Method for Manufacture of Solar Cellwith Foil Contact Point", assigned to the same assignee of the presentinvention. These solar cells typically are composed of a transparentmatrix provided with spheroidal particles of silicon, each particlehaving a p-region exposed on one matrix surface, and an n-type regionextending to an opposed matrix surface. Electrical energy is producedwhen photons of light strike the silicon sphere, inducing electrons tocross the depletion region between the two conductivity types.

Many methods of fabricating these semiconductor spheres are known in theart. In the ideal solar cell array, the spheres would be comprised ofpure semiconductor material such as silicon, have uniform mass, becrystalline and spheroidal in shape, have a high conversion efficiencyfrom solar to electrical energy, and be manufactured with highthroughput by an automated apparatus. The ideal silicon sphere has adiameter of approximately 30 mils, realizes an energy efficiency ofgreater than 10% , and has a spheroidal shape achieved throughperforming few melt cycles.

As disclosed in U.S. Pat. No. 5,069,740 to Levine, one known method offabricating silicon spheres includes first using a sieve to separateirregularly shaped metallurgical grade silicon particles by size.Particles obtained within a desired size range, are melted by aresistance heated open-hearth convection furnace operating above themelting point of silicon. The silicon particles may be heated at oneatmosphere, whereby the surface tension of silicon will cause theparticle to spheroidize, with a silicon dioxide skin being formed on thesurface of the particle during the melting process. These particles arecontrollably cooled to obtain a spheroidal crystalline particle, wherebythe silicon dioxide skin is removed using conventional grinding orchemical etching techniques, such as using an HF solution. Repeatablyheating and cooling the particle will draw impurities from the silicon,such as boron, to the silicon dioxide skin. Thus, repeatably heating andcooling the particles helps obtain a more pure silicon sphere.

The resistance heated furnaces for melting silicon particles and powdersare limited both in throughput and transport. This type of furnace doesnot directly couple heat to the silicon and, as a result, must heat thesilicon and any underlying refractory material, as well as a transporttray, up to the melting point of silicon. Not only does this reduceenergy efficiency, but the resultant delay in reaching the siliconmelting point allows for pre-oxidation, which is the growth of silicondioxide. Preooxidation of the silicon material reduces efficiency inconversion of silicon powder to fused particles, and broadens the massdistribution since some silicon is covered with silicon-dioxide, whichprevents attachment to the fused particle. Formation of silicon monoxidegas also reduces overall silicon yield. The open hearth walking beamfurnace is very limited with regard to temperature and transportadjustments.

Other known methods of fabricating consistent mass silicon spheresinvolves shotting molten purified silicon out of a nozzle, or from arotating disk. The spheres formed in this manner are highly irregular inshape, and are polycrystalline. These spheres can later be madecrystalline with the use of other processes, such as reheating thematerial above the melting point, and then controllable cooling thematerial as just described.

Another process for producing crystalline silicon spheres is disclosedin U.S. Pat. No. 4,637,855, incorporated herein by reference. Siliconspheres are fabricated by applying a slurry of metallurgical gradesilicon on to the surface of a substrate capable of maintainingintegrity at temperatures beyond the melting point of silicon. The layerof silicon slurry is then patterned to provide regions of metallurgicalgrade silicon. The substrate and silicon slurry are then heated abovethe melting point of silicon. The silicon rises and beads from theslurry to the surface as relatively pure silicon, and forms siliconspheres due to the high surface tension or cohesion of silicon. Thespheres are then controllably cooled below the melting point of silicon,and the silicon spheres then crystalize.

Several authors (ie Siemens A.G. of Munich Germany) have publishedreports in the past of attempts to generate polycrystalline siliconribbons in a continuous mode using concentrated light to melt siliconpowder. All of the processes required multiple applications of heat inorder to first consolidate the powder, then melt the consolidated sheetindividually on each side. The sheet could not be fully melted as itwould break up into small molten particles due to the surface tension ofmolten silicon. Additionally, throughputs greater than a few centimetersper minute were not achievable as the requirements or an orderedpolycrystalline structure could not be met. These previous attempts allused low flux systems as high throughput capability was never consideredpossible for producing continuous polycrystalline ribbons.

To realize solar cells of high energy conversion efficiency, it isnecessary that the semiconductor spheres be comprised of high puritymaterial. High purity silicon spheres can ultimately be obtained bystarting with either metallurgical grade, or semiconductor gradesilicon. However, the greater the impurity of the starting material, themore involved the subsequent purification processes to ultimately obtainhigh purity silicon spheres. Again, a purification process involvingadditional melt/impurity removal cycles is time consuming, requires asubstantial amount of energy, and results in lower overall siliconyield. These considerations need to be balanced against the cost of thestarting material. The cost of semiconductor grade silicon feedstock isvery expensive in relation to metallurgical grade silicon feedstock.However, the cost of off-spec semiconductor grade silicon feedstock ismore in line with the cost of metallurgical grade silicon feedstock, andeliminates the need for silicon removals.

As disclosed in the cross referenced co-pending patent application,semiconductor particles of uniform mass can be obtained by metering outpowdered feedstock into uniform mass piles of upon a refractory layer.These piles of semiconductor feedstock are then melted briefly to obtainunitary semiconductor particles of uniform mass. Silica is the preferredrefractory layer, whereby the semiconductor particles can be separatedfrom the refractory layer after the melt procedure. It is desirable toimplement this unique metering process in an automated process controlapparatus, where process parameters can be precisely controlled toobtain a high throughput of energy conversion efficient, uniform masssilicon spheres with little or no pre-oxidation.

SUMMARY OF THE INVENTION

The present invention implements a high-energy optical furnace to directfocused high intensity light to a plurality of semiconductor poweredfeedstock piles, to almost instantaneously fuse the piles efficiently.This precludes the growth of any oxide, allowing for maximum conversionof the powder to a fused particle, and limits the amount of heat lost tothe underlying refractory layer and transport surface.

The optical furnace almost instantaneously melts the semiconductorpowdered feedstock piles as they are passed by a belt conveyerthereunder, whereby the feedstock quickly freezes to form a single fusedparticle. This light is directly coupled to the silicon, with the use ofa reflective underlying refractory substrate, and the silicon particleswill wet each other rather than the substrate thus improving conversion.The feedstock can be partially or totally melted, cooled to acrystalline or polycrystalline particle and then separated from thepowdered or granular refractory layer thereunder. Subsequent remelts maybe implemented to improve sphericity and crystallinity. The piles ofsemiconductor feedstock are preferably metered out into uniform massfiles using a template according to the techniques of the copendingcross referenced patent application. This type of furnace can be rapidlyadjusted on-line with regard to power levels and transport speed.

The method according to the preferred embodiment of the presentinvention comprises defining a plurality of spaced semiconductorfeedstock piles upon a reflective refractory layer. High intensityoptical energy is directed to the plurality of semiconductor feedstockpiles, sufficient in intensity and duration to at least partially meltthe semiconductor feedstock and define a single semiconductor particle.Preferably, the refractory layer comprises a thin layer of poweredsilica spread upon a belt conveyer, this refractory layer being advancedwith the semiconductor feedstock piles under the optical furnace. Theoptical energy if focused to the silicon piles, with little heat beinggenerated in the refractory layer. Preferably, the light has a fluxdensity between approximately 400 W/cm², and 600 W/cm², whereby theconveyer medium is advanced at a rate between approximately 20 feet perminute and 30 feet per minute. In the preferred embodiment, ahigh-energy optical furnace with an elliptical reflection chamber isutilized, such as that manufactured by Vortek Industries Ltd. ofVancouver, British Columbia, Canada.

The silica refractory layer preferably has a thickness of about 1millimeter. The conveyer medium is preferably a continuous belt whichsupports and advances the silica refractory layer, as well as thesemiconductor feedstock piles, under the optical furnace and to aseparation station. This separation station separates the fusedsemiconductor particles from the silica refractory layer, whereby thesemiconductor particles are collected in one bin, and the refractorylayer is collected in another bin and returned for subsequent use. Manytypes of separation devices can be used, including angled rod screens,vibrating screens, air cyclones, etc.

In the preferred embodiment, ambient air is purged from the opticalfurnace and around the semiconductor feedstock piles when the opticalenergy is directed to the feedstock piles, thus reducing the growth ofoxide on the semiconductor material during the near instantaneous melt.Preferably, the focused optical energy is of sufficient energy tototally fuse the semiconductor feedstock piles, whereby the fusedsemiconductor material becomes substantially spheroidal.

The apparatus according to preferred embodiment of the present inventionincludes a refractory layer, and a mechanism for defining spaced pilesof semiconductor feedstock upon the refractory layer. In the preferredembodiment, this mechanism includes a template for defining uniform masspiles of semiconductor powdered feedstock upon the refractory layer. Ahigh-energy optical furnace is provided to direct and focus opticalenergy to the plurality of semiconductor powdered feedstock piles. Thisoptical furnace directs sufficient light energy to at least partiallymelt and fuse the semiconductor feedstock piles, defining thesemiconductor particles. A belt conveyer is utilized as a conveyermedium for advancing the refractory layer and the semiconductorfeedstock piles thereon to the optical furnace for fusing. Thesemiconductor feedstock preferably comprises semiconductor gradesilicon, but could also be metallurgical grade if desired. In addition,doped or undoped silicon feedstock can be utilized depending on thedesired product output. Other semiconductor feedstock materialsincluding germanium, gallium arsenide, and other well knownsemiconductor materials could be used as well. Nitrogen or argon gas isutilized for purging the optical furnace including the ambient aroundthe semiconductor feedstock piles during the fuse melt. Because thefuse/melt is almost instantaneous, whereby the semiconductor particlesalmost instantaneously freeze thereafter, and the refractory layer haslittle heat provided thereto, the powder or granules of semiconductorfeedstock wet one another rather than the refractory layer. With apurged ambient, oxide layers will not become lodged within thesemiconductor particle.

With the optical energy directed and focused to a single point upon therefractory layer, and thus to the semiconductor feedstock piles as theyare advanced therepast, a silica refractory layer of only 1 millimeterin depth is sufficient whereby the conveyer belt supporting therefractory layer will receive little or no energy and remain cool. Thatis to say, while the optical energy is sufficient to briefly raise thetemperature of the semiconductor feedstock piles to about 1,450 degreesCelsius, the temperature at the conveyer surface is less than 100degrees Celsius. In the preferred embodiment, the conveyer belt iscomprised of polymers (i.e. silicone on woven fiberglass), but thisconveyer belt could also be comprised of hard rubber or metals whichwill not buckle when heated by the temperatures experienced under therefractory layer. In the preferred embodiment, the semiconductorfeedstock piles are heated from room temperature to around 1,450 degreesCelsius in about 0.2 seconds. The optical energy almost instantly meltsthe semiconductor feedstock piles, whereby the semiconductor particlesalmost instantaneously freeze thereafter because there is inadequateheat in the pile to maintain the silicon above the melting point.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of an apparatus including a high-energyoptical furnace for fusing uniform mass piles of powered semiconductorfeedstock according to the preferred embodiment of the presentinvention; and

FIG. 2 is a graph of the preferred optical furnace flux density as afunction of the conveyer belt speed to obtain at least partially meltedsemiconductor feedstock piles.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, an automated high-throughput apparatus forforming high purity semiconductor particles according to the preferredembodiment of the present invention is generally shown at 10. Apparatus10 as viewed from left to right is seen to include a dispensing bin 12containing a quantity of powdered refractory material such as silica,and uniformly dispensing the silica 14 upon a rotating endless conveyerbelt 16 to define a uniform thickness refractory layer 18. Conveyer belt16 is advanced and regulated by a pair of opposed drive wheels 20, onedisposed at each end of the conveyer 16 as shown. At a load stationgenerally shown at 22, a template 24 is utilized automatically or byhand to meter out uniform mass piles of semiconductor powdered feedstock26 such as silicon, according to the invention disclosed in the crossreferenced co-pending patent application, the teachings of which areincorporated herein by reference. Semiconductor grade silicon feedstock26 is preferably used, although metallurgical grade feedstock can beused if desired. In addition, either doped or undoped silicon feedstockcan be used depending on the desired product output.

A high-energy optical arc furnace 30 is shown positioned over a midsection of conveyer belt 16 and including an arc lamp 32. Opticalfurnace 30 is preferable comprised of an arc furnace manufactured byVortek Industries Ltd. of Vancouver, British Columbia, Canada. Asdepicted by the arrows in FIG. 1, the high intensity optical energy oflamp 32 is reflected off an elliptical inner wall 34 and directed to asingle point 36 defined on the upper surface of refractory layer 18 andconsequently is focused upon the piles of semiconductor feedstock 26when advanced thereunder.

It is anticipated that other shapes of reflector walls 34 could be usedas well, such as parabolic or u-shaped inner wall. The optical furnacemanufactured by Vortek Industries is preferred because no other currenttechnologies provide adequate flux density for a high throughout siliconmelting process. A receiving end 38 and exit end 40 of furnace 30 isspaced approximately 1 centimeter above the surface of refractory layer18 to permit the piles of semiconductor feedstock 26 to be advancedthereunder, and fused to form unitary semiconductor particles 42. At thedistal end of apparatus 10 is seen a refractory layer collection bin 46,and a semiconductor particle collection bin 48. An angled rod screen 50is shown oriented just before the falling stream of refractory layer 18,this screen skimming the unitary semiconductor particles 42 from therefractory layer 18, and directing these particles 42 into collectionbin 48, as shown.

In the preferred embodiment, refractory layer 18 preferably has a depthof 1 millimeter. Template 24, as disclosed in the co-pending patentapplication incorporated herein by reference, includes an array ofapertures (not shown) extending through template 24. These apertures areloaded with powered semiconductor feedstock at loading station 22, theupper surface being smoothed and removed of excess powdered feedstocksuch as by doctor blading before being removed from refractory layer 16to defined the semiconductor feedstock piles 26. This metering outprocess of piles 26 by template 24 could be automated if desired, but isbeyond the teachings of the present invention.

Optical furnace 30 has a central chamber 54 which can be purged ofambient air by introducing a non-reactive gas via duct 56, such asnitrogen or argon, into chamber 54 during the fusing process. Thus, assemiconductor feedstock piles 26 are almost instantaneously fused,ambient impurities will not be present and cannot impregnate thesemiconductor piles 26 as they are fused to define unitary semiconductorparticles 42. Purging the chamber of a conventional convection furnaceis well know in the art, and is equally applicable to an optical furnaceas disclosed in the present invention. By purging the ambient about thesemiconductor feedstock piles 26 being fused, and focussing the lightenergy on the piles 26, the grains of the semiconductor feedstock powderare wetted and easily coalesce with one another. With impuritiesremoved, included oxygen, silicon dioxide is not formed on the surfaceof the particle 42, and all semiconductor material is converted to formthe single particle. Accordingly, no subsequent dean up such as grindingor chemically treating with an acid solution, such as HF, is necessary.

Referring to the graph of FIG. 2, it can be seen that the preferableoperating flux density of optical furnace 30 is between 400 and 600W/cm², with the speed of conveyer 16 advanced between 20 and 30 feet perminute. The slower the speed of the belt, the lower the required fluxdensity of the furnace to at least partially melt the piles ofsemiconductor feedstock 26. In the preferred embodiment, the maximumflux density is about 600 W/cm² with a conveyer speed of about 30 feetper second. Although these are the preferred parameters for the presentinvention, limitation to these speeds or flux densities is not to beinferred, for other parameters could be chosen as well, depending on thedesired completion of melt of the piles, and the desired uniformity ofthe melt between the plurality of semiconductor piles. One feature ofthe present invention is that the process parameters including opticalflux density and belt speed can be changed or set almostinstantaneously, with no warm-up time being required. This is aconsiderable improvement over using conventional open hearth resistanceheated furnaces.

METHOD OF OPERATION

Referring now to FIG. 1, the method according to the preferredembodiment of the present invention will be described. With driverollers 20 uniformly advancing conveyer 16 at approximately 20 to 30feet per minute, dispenser bin 12 dispenses the powdered silica 14 uponthe upper surface of conveyer 16 to define a uniform thicknessrefractory layer 18 of approximately 1 millimeter in thickness.

At semiconductor pile loading station 22, template 24 is utilized tometer out a plurality of uniform mass semiconductor feedstock piles 26.Referring to the cross referenced co-pending patent applicationincorporated herein by reference, each of the holes (not shown) oftemplate 24 are completely filled with powered semiconductor feedstock,which is preferable of semiconductor grade but could also be comprisedof metallurgical grade semiconductor powered feedstock if desired. Theexcess semiconductor feedstock is removed from the upper surface oftemplate 24 by a suitable smoothing tool or by doctor blading asdesired. Template 24 is then carefully removed from refractory layer 16to define a plurality of uniform mass semiconductor feedstock piles 26,as shown.

Conveyer 16 advances semiconductor feedstock piles 26 at a uniform rateunder the receiving end 38 of optical furnace 30, and into chamber 54.As the semiconductor feedstock piles 26 advance to point 36 withinchamber 54, the high intensity optical energy continuously radiatingfrom arc lamp 32 reflects off the elliptical walls 34 and is focused topoint 36, and thus the semiconductor feedstock piles 26. With theoptical furnace having a flux density of between 400 and 600 W/cm², andconveyer 16 advancing the semiconductor particles 26 at 20 to 30 feetper minute, the optical energy will almost instantaneously wet, melt andfuse the particles of feedstock material, in about 0.2 seconds. Themelting point of silicon is approximately 1,450 Celsius. The opticalenergy provided by lamp 32 is preferably sufficient to only accomplishan incomplete melt, whereby each of the grains of feedstock only beginsto coalesce with the adjacent grains. However, the energy is sufficientto cause the grains of feedstock to fuse to one another and form aunitary semiconductor particle 42. If desired, the optical energy and/orthe speed of the conveyer could be established to completely melt thepiles of semiconductor feedstock 26, whereby the powdered feedstockwould coalesce and completely melt.

Since the light energy is focused on the feedstock pries 26, therefractory layer 18 receives little energy and is heated very little.Thus, the feedstock granules wet on another, not the refractory layer.The chamber 54 is purged of air by introducing a non-reactive gas, suchas nitrogen or argon, via duct 56 to avoid introducing impurities intoparticle 42. Because the fuse process is almost instantaneous, there islittle or no pre-oxidation, and the conversion of the silicon is almostcompletely to form unitary particle 42, and uniform mass particles 42are realized. In addition, subsequent grinding or chemical etchingclean-up procedures are not necessary.

Conveyer 16 advances the fused semiconductor particles 42 from fusepoint 36, whereby these particles will almost instantaneously freeze toform polycrystalline particles 42 because the optical energy in the pile26 is inadequate to maintain the semiconductor material above itsmelting point. Conveyer 16 advances the semiconductor particles 42 underthe exiting end 40 of optical furnace 30, and advances the particles tothe distal end of the apparatus. Furnace 30 may have a shroud to effectthe purging process if desired.

At the distal end of the apparatus, the rod screen 50 skims the unitarysemiconductor particles 42 from the refractory layer 16 being pouredinto collection bin 46. The semiconductor particles 42 are guided intothe receiving collecting bin 48, as shown. Rod screens are well known inthe art and are preferred in the present invention, although otheralternatives are known and acceptable including vibrating screens andair cyclones.

The semiconductor particles 42 collected in bin 48 are then subsequentlyreprocessed by one or more heating and cooling (melting) cycles toremove impurities if necessary, and to obtain a crystallinesemiconductor sphere. These subsequent heating and purificationprocesses can be performed using the above process, or using processeswell known in the art, some of which are referenced in the Background ofthe Invention section of this application. If desired, the semiconductorparticles 42 could be reprocessed by advancing them under the opticalfurnace 30 as just described, at the same rate or a different rate, andat the same or different optical flux density just described. Theobtained semiconductor spheres are ultimately implemented in a solarcell.

According to the preferred embodiment of the present invention, a highthroughput apparatus and method is provided. Uniform mass semiconductorparticles 42 are obtained without introducing impurities into theparticle during the optical fusing process. The optical furnace 30 ispower efficient since there is no warm up time for the furnace, andenergy can be directly applied to mainly the piles of semiconductorfeedstock without any significant energy being directed into therefractory layer 16. Thus, both a waste of time and energy is avoidedusing an optical furnace, as compared to a conventional convectionfurnace.

The process parameters including rate at which conveyer 16 is advanced,and the flux density at which optical furnace 30 operates, can also beprecisely and instantaneously controlled. This permits the control ofthroughput, and of the texture of semiconductor particles 42 whetherthey be partially or totally melted during the fusing process. When puresemiconductor feedstock is utilized to define piles 26, a puresemiconductor particle 42 is realized, and when which implemented in asolar cell array, realizes a high efficiency solar cell array with anenergy conversion well in excess of 10%. While silicon is the preferredsemiconductor feedstock processed according to the present invention,other well known semiconductor feedstock materials could be utilized aswell including germanium and galium arsenide if desired. In thepreferred embodiment, semiconductor particles 42 have a diameter ofapproximately 30 mils.

Silica is the preferred material for refractory layer 18. However, otherrefractory materials could be used as well, including quartz boats ifdesired. However, silica is ideal in that a very smooth reflective layercan be defined for supporting semiconductor feedstock piles 26, isrelatively inexpensive, and can be easily reprocessed by collecting incollection bin 46, as shown.

In the preferred embodiment, more than 200,000 semiconductor particles42 can be defined per minute in a 1 foot wide melt furnace. Of course,this throughput is limited only by the dimensions and process parametersassociated with the present invention, and higher throughputs could berealized by using a larger conveyer, a larger template, and/or usingoptical furnace with a higher flux density.

Because the process of the present invention is truly automated, theassociated cost for manufacturing high-quality semiconductor particlesis very appealing. Highly uniform semiconductor particles are obtained,of high purity and consistency. The present invention overcomes thedrawbacks associated with implementing conventional convection furnaces.

Though the invention has been described with respect to a specificpreferred embodiment, many variations and modifications will becomeapparent to those skilled in the art upon reading the presentapplication. It is therefore the intention that the appended claims beinterpreted as broadly as possible in view of the prior art to includeall such variations and modifications.

We claim:
 1. A method of forming semiconductor particles, comprising thesteps of:a) defining a plurality of spaced piles of semiconductorfeedstock upon a refractory layer; and b) directing optical energy tosaid plurality of semiconductor feedstock piles of sufficient energy toat least partially melt said semiconductor feedstock and define saidsemiconductor particles, wherein said method further comprising the stepof defining said refractory layer upon a conveyor medium, and advancingsaid conveyor medium to advance said semiconductor feedstock piles pastsaid directed optical energy.
 2. The method as specified in claim 1further comprising the step of directing said optical energy with a fluxdensity between approximately 400 W/cm² and 600 W/cm².
 3. The method asspecified in claim 1 comprising the step of advancing said conveyermedium at a rate between approximately 20 ft/minute and 30 ft/minute. 4.The method as specified in claim 1 comprising the step of forming alayer of silica on said conveyer medium as said refractory layer.
 5. Themethod as specified in claim 1 comprising the step of utilizing siliconas said semiconductor feedstock.
 6. The method as specified in claim 1comprising the step of utilizing doped said semiconductor feedstock. 7.The method as specified in claim 4 comprising the step of defining saidsilica layer with a thickness of about 1 mm.
 8. The method as specifiedin claim 1 comprising the step of utilizing a template to define saidsemiconductor feedstock piles.
 9. The method as specified in claim 1comprising the step of utilizing an optical arc furnace to direct andfocus said optical energy to said semiconductor feedstock piles.
 10. Themethod as specified in claim 4 comprising the step of separating saidsemiconductor particles from said silica refractory layer.
 11. Themethod as specified in claim 10 comprising the step of collecting saidsilica refractory layer after said separation from said semiconductorparticles and reprocessing said silica refractory layer.
 12. The methodas specified in claim 1 further comprising the step of purging ambientair from about said semiconductor feedstock piles when directing saidoptical energy thereat.
 13. The method as specified in claim 1comprising the step of directing said optical energy of sufficientenergy to totally fuse said semiconductor feedstock piles.
 14. Themethod as specified in claim 13 comprising the step of directing saidoptical energy of sufficient energy that said semiconductor feedstockpiles fuse and form generally spheroidal said semiconductor particles.